It originally appeared in the June 2009 issue of DISCOVER Magazine. (I just "discovered" it ...) The introduction does a great job of describing the crossroads we're at today as science and public opinion meet:

"In the list of world challenges, global warming might be at once the most alarming and the most controversial. According to some predictions, climate change caused by human activity could cause mass extinction in the oceans, redraw the planet’s coastlines, and ravage world food supplies. At the same time, a significant portion of the American public questions whether global warming will really cause any major harm; many still doubt that human-driven warming is happening at all."

Here are a few highlights of the discussion:

"I spend a lot of time studying the ice sheets at the bottom of the planet—how they form and how they collapse. The poles are like the planet’s air conditioner. When things are working well, the poles keep the planet nice and cool and we don’t think about it. When things stop working, the poles can start to melt and there’s a puddle on the floor. Today both poles are getting warmer; in Greenland and Antarctica you can see the surface of the ice dropping, and you can see there’s less mass when you measure the ice from space. The process has been ongoing, but it looks like it’s happening faster than it was. We know the ice sheets have come and gone in the past. Why is this any different? One of the most compelling reasons is that in the past the ice sheets from the two poles didn’t move together—one would lead and the other would follow. This time, both the north and south are spewing ice into the global ocean, accelerating at the same time."

[... the Earth got warm in the past, too] "but it got warm over millions of years, and ecosystems had a chance to adapt. What we’re seeing are rates of increase in greenhouse gases and warming that exceed natural rates by a factor of 100. So what we’re doing is really unusual when seen from a geologic perspective.

[Humans are doing in centuries what natural processes do over millions of years?] "Yes, and the other timescale mismatch is that what we do over the next decades will affect life on this planet for hundreds of thousands of years, if not millions of years. We are at a critical juncture in earth history. If we don’t do the right thing and there are geologists around 50 million years from now, they’ll be able to look at cores and see the remnants of a civilization that developed advanced technology but didn’t develop the wisdom to use it wisely."

"To me the most compelling evidence [that human behavior is actually warming the planet] is the fact that the stratosphere — the upper atmosphere — is cooling while the lower atmosphere and the land surface are warming. That’s a sign that greenhouse gases are trapping energy and keeping that energy close to the surface of the earth. I mentioned that in ocean acidification, you actually see animals that should make shells unable to make shells anymore. You could demonstrate the same kind of effect in a bell jar in the lab. There is a level of certainty about it."

— Ken Caldeira, a professor at Stanford and staff member in the department of global ecology at the Carnegie Institution of Washington

"One of the most remarkable achievements of the 20th century was the way we were able to increase the global food supply in pace with unprecedented population growth. We will have to raise the food supply another two times to feed all of the people that we think will be alive by the latter third of the 21st century. We have reason to be somewhat sanguine about doing it if climate stays more or less the same, but how will we do it with the climate change? Based on our simulations and on 25 years of research, what bothers us most is that in the tropics, where the majority of poor people live today, crops are currently raised at temperatures pretty close to their photosynthetic optimums."

— Bill Easterling, Dean of the College of Earth and Mineral Sciences at Pennsylvania State University

The emails tell the story of how the data has been manipulated. GLOBAL WARMING IS A HOAX TO MAKE A FEW PEOPLE RICH ie AL GORE WHO HAS INCREASED HIS WEALTH BY $99 MLLION DOLLARS SINCE 2000.
People can not affect the climate.
TO THE PERSON THAT THINKS SOCIALISM IS A GOOD THING, STUDY HOW BRADFORD THE GOVERNOR OF THE PLYMOUTH COLONY SAID PEOPLE WERE NOT WORKING WHEN IT WAS OPERATED AS A COMMUNE. HE GAVE EACH PERSON A SEPARATE PLOT OF LAND TO WORK AND THAT WAS WHEN FREE ENTERPRISE STARTED AND THE COLONIES BECAME SUCCESSFUL AND WERE ABLE TO PAY THE INVESTERS THAT STARTED THEM.
SOCIALISM DOES NOT WORK AND THE HEALTH PLAN PROPOSED IS SOCIALIZED MEDICINE AND WILL NOT WORK.
KEEP FREE ENTERPRISE AND FIND A WAY TO GET MORE PEOPLE INSURED THROUGH THE SYSTEM WE HAVE.
FRAN

ccm989

11/24/2009 7:09:32 AM

Its sad to read how many denials there are about Global Warming. I think the main reason people keep denying the existence of Global Warming is that they don't want to give up their luxury SUVs, they don't want to stop eating beef and they don't want to be responsible for their children's future. Pretty sad. If you care about this planet at all, then get off your fat butt and start cutting down on your own waste, be responsible for your own excess use of gas and beef, recycle everything and teach your children that the world is not a garbage can. If we don't stop Global Warming now, our children have no future. And we'll have no one to blame except the lazy fat deniers who refused to give up their Hummers.

Linda Pierucki

11/23/2009 12:23:33 PM

Perhaps when people get to see the huge ftp files of hacked emails and documents that surfaced this week from Great Britain, they will clearly see that much of the data has been massaged and doctored to support global warming where there is none. The Universities and 'scientists' involved have admitted these are their actual files. The documents make it quite clear that their climate models are faulty and that they've been forced to cover up the cooling trend over the last ten years. They also show who has been paying for this so-called science and, thus, who will benefit from it. Hint: it isnt you or me! A report is being prepared that compiles the files in a readable document and will be distributed to legislators, who will then have to either back off these insane claims or come right out and say the global warming scam/Cap & Trade is actually a wealth-redistribution scheme and designed to enrich big business at the expense of the American citizens.It has nothing to do with any actual human-caused activities. In front of this report, here come the same 'scientists' with their pants around their knees doing damage control! Media has, as usual, assigned their most inane talking heads to make a small news report on this without having the vaguest idea what it is all about. So, wait until you see the full report before deciding this is the real deal.

George Works

11/23/2009 7:47:18 AM

I'm a retired engineer and member of AAAS, and I follow the climate science pretty closely. I'd like to make a few points.
Nearly all climate scientists today agree that there is global warming, that it is largely caused by human activity, and that it is likely to be bad for us. There are a lot of details left to be understood, as in most scientific fields.
We have already changed the climate, and it will take a long time to reverse even if we could stop burning fossil fuels today. Carbon dioxide, the main cause of warming, stays in the atmosphere for a half-life of about 200 years. The CO2 from your car trip today will still be warming the earth a century from now.
While we should do everything reasonably possible to reduce CO2 emissions we probably can't stop the increase in CO2 levels, at least not for several decades. It takes a long time to replace all the fossil-fuel powered agriculture, transportation, manufacturing and buildings in the world. And building new infrastructure emits more CO2.
So here we are, and there are no easy answers. We can all help by by reducing our energy use, and by buying as little "stuff" as we can. Keeping the family small helps too.

Steffanie

9/24/2009 7:12:21 PM

I personally believe that it would take a lot for of to mess up something that God has made, and arrogant of us to think we can fix it. If we broke it, I'm pretty sure he would of already found a way to fix it. Just look at what happened with Adam and Eve, God fixed that one! THis is no different.

AnnanAmos

9/21/2009 6:25:08 PM

The Jury being out is indeed often a lame excuse to ignore a problem. The fact of the matter is that mankind has had a negative impact on the environment, and to think anything otherwise is a monumental folly. The amount of carbon dioxide being released by motor vehicles alone should have been a concern, nevermind the amount that is released by industrial applications. The reason why is pretty simple, and it's a basic that just about anyone knows.
The atmosphere, i.e. the air we breathe, is comprised largely of nitrogen (79%) oxygen (19%) and other gases. Now, that mixture of air is more or less what we, as humans, depend on to live. It is a known fact that carbon dioxide and carbon monoxide, though they do contain oxygen, are harmful to people, to plants, and to other organisms. (Except bacteria that are anaerobic - but to heck with them. They don't need oxygen? Their being smug.) Therefore, we naturally want to keep the emission of those gases to a bloody minimum, don't we?
Part of the other side of the argument is that the Earth does (and it does) go through natural cooling and warming cycles. For instance, it's relatively common knowledge that the Earth came out of an Ice Age between 10 and 20,000 years ago or so. Given that, some warming of some kind would be expected. That being said, the rate is the disturbing part, and that would therefore dictate that human beings are having far more of an impact that we are willing to acknowledge at this point. Essentially, most of the completely against argument comes from people that would have their industries somewhat threatened by having to discontinue their current practices, and having to find something else to do. Essentially, it's selfish. A little more money in someone's pocket...does not, in any way, trump the interests of this planet, and therefore, our species. We WILL, rest assured, have to find another planet suitable to live on. We WILL have to start colonizing spa

Roger_23

9/17/2009 6:39:57 PM

"Previous changes took millions of years". Tell that to the frozen mammoths.
"Both poles are melting". Not so. Antarctic ice sheet is thickening. When I pointed this out, I was told "global warming has increased the moisture in the air so there is more precipitation". (Apparently the Arctic was not informed of this effect. The ice Arctic melted around 1904 so that Amundssen managed to sail the North West Passage, yet it is now cause for alarm!)
One side of the Greenland ice sheet is melting, the other is thickening. No one seems sure what Greenland is actually doing.
Now these measurements are being denied.
"Stratosphere cooling while troposphere heating up". Not true. Only very close to the surface has there been tropospheric warming and this has lagged surface warming, not led it.
In addition, ocean levels have not risen despite claims to the contrary. Rises can only be quoted if you are selective with your choice of reference tide gauges, taken overall there is no rise.
Medieval warm period was warmer than now (grapes in Canada, wheat in Greenland, vineyards in England etc).
The reference figure of around 290ppm for pre-industrial CO2 was arrived at by ignoring most of the chemically determined CO2 measurements. If they are all taken into account the figure rises to over 335ppm, not much below the present.
The baseline for atmospheric CO2 is Mauna Loa - on top of an active volcano and not far from at least 2 other ones! The figures are "corrected" to compensate! (This when they have Cape Grimm in Tasmania available)
If you look at the spectral absorption bands for CO2 and the long wave radiation from the earth, CO2 is also a lousy greenhouse gas. Anthropogenic CO2 accounts for 0.11% of greenhouse gases if water vapor is taken into account. IPCC figures leave the water vapor out, despite it being a far more powerful greenhouse gas than CO2 and in fact completely overwhelming the effect of CO2

DrFood

9/16/2009 4:31:51 PM

Thanks for this, but I think that there are few people remaining who could be convinced who don't already realize that global climate change is real, it is caused by human activity, and it can no longer be stopped, only lessened in its impact.
The folks who insist that "the jury is out" on global climate change are often the same folks who think that health care reform is a step down a slippery slope to evil socialism and even overlap those few souls who think that Saddam Hussein really did have weapons of mass destruction, but they were spirited away into Syria, probably by Osama bin Laden.
I await the arguments against the validity of thousands of scientific papers--it is sometimes amusing, although if you think hard about what we could have accomplished if so much sand had not been thrown into the already rusty gears of collective action (better CAFE standards, anyone?) then it gets rather depressing very fast.

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